1. Field of the Invention
The present invention relates to a fast printing method and apparatus for a laser beam printer, and more particularly, to a printing method by which documents can be printed at an increased speed when a user selects a fast printing mode.
2. Description of Related Art
The printing speed of a laser beam printer depends on the output speed of a printer engine, measured mostly in pages per minute (PPM).
FIG. 1A is a waveform diagram of video pulses provided to a conventional printer for printing documents and FIG. 1B is a diagram illustrating a dot arrangement corresponding to the waveform of the video pulses shown in FIG. 1A. The conventional printer includes a video controller and a printer engine. The video controller outputs video pulse signals for document images, and the printer engine receives the video pulse signals and prints the document images on sheets of paper.
As shown in FIGS. 1A and 1B, if a video pulse signal having a waveform shown in FIG. 1A is provided to a laser scanning unit (LSU) located in the printer engine, a laser beam is irradiated on a drum by the LSU. Then, toner particles are fused onto the drum, thus forming dots on the drum, as shown in FIG. 1B. Thereafter, the dots are finally printed on a sheet of paper.
In other words, if video signals having uniform pulses are sequentially input into the LSU for the dots of FIG. 1B to be printed out on a sheet of paper, a certain amount of toner is fused onto the drum to form each of the dots. Each of the dots to be printed out has a value of ‘1’ or ‘0’. When a dot has a value of ‘1’, one pulse is generated. On the other hand, when the dot has a value of ‘0’, no pulse is generated.
In FIG. 1A, each horizontal line indicates a print line. A series of video pulse signals is generated for each print line, and then the series of video pulse signals is scanned in a specified area using a horizontal synchronization signal (HSYNC). The location of each print line is determined by rotating a motor connected to the drum, the frequency of which depending on the printer engine's speed.
However, in the above-described conventional printing method, documents can only be printed at a specified printing speed, irrespective of whether or not the documents contain rather complicated forms and contents to be printed. Therefore, materials, such as texts, which are considered easy to print, can never be printed out at faster speeds than the specified printing speed, even though a user wants to quickly print the documents.